This invention relates to power converters which transform electric energy from a polyphase A.C. or a D.C. source to a recurrent train of discrete quantities of energy. These quantities of energy can be utilized in pulse forming networks which feed a pulse energy demanding load for a recurrent succession of operation. Typical loads of this kind are pulsed laser or radar systems.
Static power converters of the kind as just described are well known in the art. One representative kind consists of a cascaded succession of (1) a three phase full wave rectifier, (2) a low freqeuncy D.C. filter to smooth the remanents of the A.C. content in the rectified A.C. voltage, (3) a regulating type of D.C. to D.C. converter with a built in voltage scaling device such as a transformer and (4) an output filter to smooth the effects of the internal operation of the aforesaid D.C. to D.C. converter. The output power of the aforesaid output filter is then used to charge a discharge capacitor which, at times, is isolated from the above described source of supply and then connected to a pulse energy load, such as a laser system. The above power converter system performs a valuable and needed function in present day technology.
This present day state of the art system also embodies passive low frequency filters to smooth the A.C. ripple content of the rectified A.C. power and of dissipative waveshaping of the charging voltage for the aforesaid charging capacitor. The system also requires accurate feedback control electronics to stabilize the voltage for the aforesaid discharge capacitor. Passive low frequency filters are inherently bulky, have a heavy physical weight, and are costly. The efficiency of charging capacitors via a dissipative-resistive element is limited to 50 percent at best with the balance of energy being dissipated, or transformed to heat in the aforesaid resistive elements. Thus more energy is transformed into heat in this process than transferred for a useful purpose to the discharge capacitor. The amount of this heat dissipation in the series resistive element of a capacitor charging process is also documented in my doctorate dissertation "A Class of Nonlinear Active Filter for Electric Energy Conversion", Cornell University, 1965. The above resistive element is often partially or wholly embodied in power controlling solid state elements, such as power transistors. The need to let the converter's output voltage follow the replica of a reference signal, which often takes, partially, the form of a ramp function, requires close guidance of the power flow by way of a feedback control system with all of the associated stability problems. These problems cause a certain degree of complexity of the electronic control system.
The state of the art power converters for pulsed loads, as described above, thus involve substantial bulk of apparatus caused by low frequency filters. Substantial heat is also developed requiring adequate provisions for cooling and thus entailing physical bulk of apparatus. In addition, a complex electronic control system is required for dynamic stabilization, thus raising functional hazards.